A gear pump typically includes a pump cylinder, and a driving gear and a driven gear received in the pump cylinder. The driving gear and the driven gear are meshed with each other. When rotating, the driving gear and driven gear continuously engage and disengage, resulting in a change in a work volume formed between the pump cylinder and the meshed gears, such that the fluid is delivered or pressurized. The two gears and pump cylinder are usually required to be intimately assembled to prevent the fluid from directly flowing through the gap between teeth of the two gears or through the gap between the gears and the pump cylinder. However, each component has a certain tolerance. During operation, collision between the gears and the pump cylinder may occur which would generate noise.